Mercury can be present in trace amounts in all types of hydrocarbon streams such as natural gas. The amount can range from less than 1 ppbw (parts per billion by weight) to over a thousand ppbw depending on the source. Methods have been disclosed to remove mercury from liquid hydrocarbon feed. U.S. Pat. Nos. 5,281,258 and 5,223,145 disclose methods of removing mercury from natural gas streams by selective adsorption in fixed adsorbent beds. U.S. Pat. No. 4,474,896 discloses using polysulfide based absorbents to remove elemental mercury (Hg0) from gaseous and liquid hydrocarbon streams.
There are also a number of commercially available processes and products for the removal of elemental mercury Hg0 from hydrocarbon streams including but not limited to ICI Synetix' Merespec™ fixed bed absorbents, UOP's HgSIV™ regenerative mercury removal adsorbents, and Johnson Matthey's Puraspec™ and Puracare™ granulated absorbents for the removal of mercury from gaseous hydrocarbon streams. Adsorption technology generates a mercury-containing spent adsorbent, which is hazardous solid waste for disposal.
Production of oil and gas is usually accompanied by the production of water. The produced water may consist of formation water (water present naturally in the reservoir), or water previously injected into the formation. As exploited reservoirs mature, the quantity of water produced increases. Produced water is the largest single fluid stream in exploration and production operations. Every day, U.S. oil and gas producers bring to the surface 60 million barrels of produced water.
There is a need for improved methods for the removal of mercury from gaseous hydrocarbon streams, and particularly methods wherein produced water can be used/recycled.